Macrophage ablation impairs the formation of hybrid hepatocytes in tomm22 MO-injected larvae. (A) Confocal single-optical section images showing the expression of mpeg1:Dendra2 (green, macrophages) and fabp10a:CFP-NTR (blue, hepatocytes) in the liver at 5 dpf. Arrows point to macrophages. (B) Confocal single-optical section images showing the expression of mpeg1:Dendra2 (green), Tp1:H2B-mCherry (red), and fabp10a:CFP-NTR (blue) in the liver at 7 dpf. Arrows point to macrophages in the control liver; arrowheads point to a macrophage engulfing a hepatocyte in tomm22 MO-injected larvae. (C) Fluorescence images showing macrophage NTR-mCherry expression before and after metronidazole (Mtz) treatment. Mtz (10 mM) was treated from 4 to 7 dpf. Note the great reduction in the number of NTR-mCherry+ macrophages in the Mtz-treated larvae at 7 dpf compared with the DMSO-treated controls. Lateral views, dorsal up, anterior to the left. Scale bar: 250 μm. (D) Scheme illustrating the period of Mtz treatment and harvest stage for macrophage ablation for (E–I). (E) Confocal single-optical section images showing the expression of Tp1:H2B-mCherry (red) and Hnf4a (gray) in the liver at 7 dpf. Arrows point to H2B-mCherry/Hnf4a double-positive cells; arrowheads point to Hnf4a single-positive cells. (F) Graph showing the percentage of H2B-mCherry− cells among Hnf4a+ cells. Red marks indicate the larvae shown in (E). (G) Confocal single-optical section images showing the expression of fabp10a:mAGFP-gmnn (green), Tp1:H2B-mCherry (red), and Hnf4a (gray) in the liver at 7 dpf. Arrows point to mAGFP-gmnn/H2B-mCherry/Hnf4a triple-positive cells; arrowheads point to mAGFP-gmnn+/H2B-mCherry−/Hnf4a+ cells. (H) Graph showing the percentage of fabp10a:mAGFP-gmnn+ cells among Hnf4a+ cells. Red marks indicate the larvae shown in (G). (I) Graph showing the percentage of H2B-mCherry+ or H2B-mCherry− proliferating Hnf4a+ cells. Red marks indicate the larvae shown in (G). n indicates the number of larvae examined. (J) Confocal single-optical section images showing the expression of WRE:d2GFP (green, Wnt activity) and Tp1:H2B-mCherry (red) in the liver at 6 dpf. Anti-GFP antibody was used to reveal WRE:d2GFP expression. Note the complete absence of hepatic d2GFP expression in the XAV939-treated, tomm22 MO-injected larvae, whereas its faint expression in macrophage-ablated, tomm22 MO-injected larvae. Scale bars: 20 μm, except (C); error bars: ±SEM.
|